(1) Field of the Invention
The present invention relates to a process for producing phenol resin and epoxy resin, which are excellent in color tone and which are derived from unsaturated cyclic hydrocarbon such as dicyclopentadiene together with phenol.
More particularly, the invention relates to a process for producing phenol resin and epoxy resin which are excellent in the resistance to heat, moisture and cracking or the like, so that they are useful as electrically insulating materials, particularly as resins for sealing or encapsulating semiconductors and resins for laminated plates. Furthermore, both the resins are excellent in external appearance and in marking property owing to their good color tone or color density (hereinafter sometimes referred to as simply xe2x80x9ccolorxe2x80x9d).
(2) Prior Art
In recent years, with the rapid progress in scientific technology, especially in electronic industry, requirements for properties of several products and their raw materials becomes gradually severer. Among them, the improvement in semiconductor technology is remarkable. With the progress in complexity of semiconductor memory, electronic circuits become minute and chip sizes become large. Moreover, mounting method is shifted from through-hole mounting to surface mounting. However, in automation lines of surface mounting, several troubles take place. For example, when a lead wires are soldered, semiconductor packages suffer from rapid change of temperature, which causes cracking in molded resin parts for sealing semiconductors, and interfaces among lead wires and resin are damaged to cause deterioration of moisture-proofing property.
In order to prevent the moisture-proofing property from deterioration, a method to increase the amount of filler by changing its particle shape is proposed. However, with this method, elasticity of resin increases, so that the resin is liable to suffer cracking due to thermal shock. Therefore, in order to reduce the thermal shock in semiconductor package when it is immersed in a solder bath, methods of modifying resin composition are proposed, such as the addition of silicone compounds or thermoplastic oligomer into the resin, or modification with silicone. However, in all of these methods, molded products suffer cracking after they are immersed into a solder bath, so that reliable resin compositions for sealing semiconductor cannot still be obtained.
In resin compositions for sealing semiconductor, those used as hardening agents are phenol resins such as phenolic novolak resin and cresol novolak resin, and the one used as a main component is epoxy resin having cresol novolak structure. However, when these resins are used, moisture-proofing property of semiconductor package is impaired to cause inevitably the above-mentioned cracking during immersion in a solder bath.
In recent years, therefore, in order to improve the thermal resistance of resin composition for use in sealing semiconductor, investigations have been conducted for improving phenol resins as raw materials of epoxy resins and their hardening agents. In Japanese Patent Application No. H03-66919, the present inventors proposed a phenol resin obtained by reacting phenol and an unsaturated polycyclic hydrocarbon compound having two or more carbon-carbon double bonds such as dicyclopentadiene, and they reported that the phenol resin can solve the above problem when it is used as a raw material of epoxy resin and its hardening agent.
It is widely known that the phenol resin modified with dicyclopentadiene can be produced with the use of boron trifluoride or boron trifluoride-phenol complex. However, it has been regarded as a problem that the phenol resins produced by this method are colored into dark brown so deeply that the external appearance of molded products are very poor, and the epoxy resin obtained by reacting the above resin with epihalohydrin is similarly colored into dark brown. When the epoxy resin is used as a raw material of sealing resin compositions, characteristics such as moisture-proofing property and thermal resistance can be improved. But on the other hand, there has been a problem in that the marking property of the compositions is so poor that operating efficiency is remarkably lowered in the process for production.
In Japanese Laid-Open Patent Publication No. H08-53539, a producing method with improving colors of epoxy resins is disclosed. However, the colors are still not satisfactory. Furthermore, this method has problems in that it requires freeze-drying in several times and degassing of raw materials, so that the operating process is complicated and it requires much labor, and in addition, the cost for production is high.
Further, in Japanese Laid-Open Patent Publication No. H07-252349, a method is presented for improving colors of resins by dissolving refined resins in a solvent and then contacting them with inorganic porous materials. However, there is a similar problem that the operating process is complicated and requires much labor, and production cost is expensive.
It is, therefore, the primary object of the present invention is to propose a method for producing phenol resin having desirable color tone by reacting hydroxyl group-containing aromatic compound and unsaturated cyclic hydrocarbon in the presence of an acid catalyst. Another object of the invention is to provide a method for producing epoxy resin that is excellent in color tone by using the above phenol resin.
The present inventors have carried out investigation to solve the above problems, as a result, they have found out the following fact in the method for producing phenol resin by reacting hydroxyl group-containing aromatic compound with unsaturated cyclic hydrocarbon in the presence of Friedel-Crafts acid catalyst. That is, phenol resin having good color tone can be obtained by adjusting the moisture content in a reaction system during reaction, and in addition by adjusting the concentration of Friedel-Crafts catalyst. Furthermore, epoxy resin having good color tone can be obtained by adding glycidyl group to the obtained phenol resin in the presence of base catalyst, removing residual catalyst and refining by distilling off unreacted epihalohydrin. As a result, they have accomplished the present invention.
Thus, a first aspect of the present invention is a process for producing a phenol resin having good color tone, which process comprises reacting hydroxyl group-containing aromatic compound and unsaturated cyclic hydrocarbon under the conditions that the moisture is 100 ppm or less and the concentration of Friedel-Crafts catalyst is 0.07 mass % or less in a reaction system.
A second aspect of the present invention is a process for producing a phenol resin described in the first aspect, wherein a hydroxyl group-containing aromatic compound is the one selected from a group consisting of monohydric and dihydric phenols and bisphenol, and an unsaturated cyclic hydrocarbon is dicyclopentadiene.
A third aspect of the present invention is a process for producing a phenol resin described in the first aspect, wherein Friedel-Crafts catalyst is boron trifluoride.
A fourth aspect of the present invention is a process for producing epoxy resin having good color tone, which process comprises reacting the phenol resin described in a first aspect and epihalohydrin in the presence of base catalyst, then removing catalyst residue and removing unreacted epihalohydrin.
The phenol resin obtained in the first aspect of the present invention gives absorbance of 1.0 or lower at wavelength of 350 nm in a dioxane solution of 2 mass %, and the color tone is good.
In other words, it is possible to obtain a phenol resin that gives absorbance of 1.0 or lower at wavelength of 350 nm in a dioxane solution of 2 mass % by the present method. It comprises reacting hydroxyl group-containing aromatic compound and unsaturated cyclic hydrocarbon having two or more carbon-carbon double bonds in the presence of Friedel-Crafts catalyst.
Furthermore, an epoxy resin obtained according to the fourth aspect of the present invention gives absorbance of 0.8 or lower at wavelength of 350 nm in a dioxane solution of 2 mass %, and the color tone is good.
In other words, it is possible to obtain an epoxy resin that gives absorbance of 0.8 or lower at wavelength 350 nm in a solution of 2 mass % in dioxane by the present method. It comprises reacting the phenol resin that is obtained by reaction of hydroxyl group-containing aromatic compound with unsaturated cyclic hydrocarbon having two or more carbon-carbon double bonds in the presence of Friedel-Crafts catalyst, with epihalohydrin in the presence of a base.
In the following, the present invention will be described in more detail.
In the present process for producing an epoxy resin having good color tone, phenol resin is produced in the first place as an intermediate material according to the following process.
That is, phenol having phenolic hydroxyl group and unsaturated cyclic hydrocarbon having two or more carbon-carbon double bonds are allowed to react in the presence of Friedel-Crafts catalyst.
Exemplified as unsaturated cyclic hydrocarbons used as raw materials for the phenol resin in the present invention are dicyclopentadiene, 4-vinylcyclohexene, 5-vinylnorborna-2-en, 3a, 4, 7, 7a-tetrahydroindene, xcex1-pinene, and limonene. These compounds can be used in a mixed. Dicyclopentadiene is favorable particularly, because the obtained resin is excellent in thermal resistance, moisture-proofing property and mechanical characteristics.
Commercially available dicyclopentadiene often contains impurities to some extent. However, it can be used without any trouble, as long as its purity is 80 mass % or higher, preferably 90 mass % or higher.
Hydroxyl group-containing aromatic compounds are not particularly limited as long as they have hydroxyl groups directly connected to aromatic rings. Exemplified as favorable ones are monohydric phenols such as phenol, o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphenol, o-propylphenol, m-propylphenol, p-propylphenol, p-sec-butylphenol, p-tert-butylphenol, p-cyclohexylphenol, p-chlorophenol, o-bromophenol, m-bromophenol, p-bromophenol, xcex1-naphthol and xcex2-naphthol; dihydric phenols such as resorcin, catechol, hydroquinone, 2,2-bis(4xe2x80x2-hydroxyphenyl)propane, bis-(hydroxyphenyl)methane, bis(hydroxynaphthyl)methane, tetramethylbiphenol and biphenol; trihydric phenols such as tris(hydroxyphenyl)methane, and the mixtures of them.
Among them, phenol, o-cresol, m-cresol, xcex1-naphthol, xcex2-naphthol and 2,2-bis(4xe2x80x2-hydroxyphenyl)propane are desirable because they are economically efficient and easy to produce. They can also be used as a mixture.
In the reaction of unsaturated cyclic hydrocarbon and hydroxyl group-containing aromatic compound, molecular weight and melt viscosity of the obtained phenol resin can be adjusted arbitrarily by changing the molar ratio of both components. However, the ratio of (hydroxyl group-containing aromatic compound)/(unsaturated cyclic hydrocarbon) in the range of 1 to 20 (in molar ratio) is generally preferable. Particularly when melt viscosity must be lowered, the ratio of (hydroxyl group-containing aromatic compound)/(unsaturated cyclic hydrocarbon) in the range of 1 to 15 (in molar ratio) is preferable.
When epoxidation is carried out by using phenol resin having low melt viscosity, epoxy resin having low melt viscosity is obtained. Both the resins can be filled with large quantities of fillers, so that they have preferably low coefficients of linear expansion and high water resisting property.
When catalyst is used in a small quantity, the molar ratio of (hydroxyl group-containing aromatic compound)/(unsaturated cyclic hydrocarbon) of 7 to is preferable.
As Friedel-Crafts catalysts used for producing the phenol resin in the present invention, those are used, which have good activities and easiness of removing. That is, they are metal halides such as boron trifluoride, their complex catalysts such as boron trifluoride-ether complex, boron trifluoride-phenol complex, boron trifluoride-water complex, boron trifluoride-alcohol complex and boron trifluoride-amine complex, and mixtures of these. Among all these, boron trifluoride, boron trifluoride-phenol complex and boron trifluoride-ether complex are desirable.
By the way, boron trifluoride-phenol complex and the like are commercially available in a form of phenol solution. In the present invention, such a phenol solution can be used. Further, when complex catalysts such as boron trifluoride complex are used, there are two ways available. The one is to use previously prepared catalysts just like the above-mentioned commercial phenol solution of boron trifluoride, and the other is to supply a reaction system with boron trifluoride and ligand separately and form a complex in the system for use in reaction.
In producing phenol resins in the present invention, water content is adjusted previously, then reaction is carried out under the condition comprising a concentration of Friedel-Crafts catalyst of 0.07 mass % or less. Here, xe2x80x9cconcentration of catalystxe2x80x9d in the present invention means that in a reaction system, and Friedel-Crafts catalyst means that exclusive of ligands which constitute complex. For example, when boron trifluoride-phenol complex is used, concentration of catalyst is represented by the amount of boron trifluoride only. Needless to say, it is catalysts containing ligands that are used in a reaction system.
By the way, in the present invention, a mode of reaction that reactant itself serves as a reaction solvent is preferable, though other reaction solvents can be used. In the latter case, concentration of catalyst means that in a reaction system including the reaction solvent.
As to reaction style, either type of batch and continuous flow can be used. In the batch type, the order and the method of adding reactants are not specially restricted. As mentioned later, the method of adding at least unsaturated cyclic hydrocarbon into a reaction system little by little can be used. For example, into a reaction vessel previously supplied with hydroxyl group-containing aromatic compound and, if necessary, solvent, can be added slowly unsaturated cyclic hydrocarbon. Catalysts may be added slowly just like unsaturated cyclic hydrocarbon, and also the whole amount may be added previously.
When at least one of reactants is added little by little in a batch type reaction as above, concentration of catalyst can increase temporarily at the beginning of reaction depending on the modes of supplying catalyst. In the present invention, it is preferable to keep the concentration of catalyst as low as possible, though the temporary high concentration at the beginning of reaction can be allowed. However, in this case also, it is preferable to keep the catalyst concentration 0.10 mass % or less.
In these cases of the present invention, the xe2x80x9cconcentration of catalystxe2x80x9d means the concentration of catalyst at the final step of supplying raw materials, that is, the concentration at the point when the supply of the whole reactants and catalysts are completed. Further, concentration of catalyst can also increase in the latter period of reaction, and in this case also, the xe2x80x9cconcentration of catalystxe2x80x9d means that at the point when the supply of the whole reactants including catalysts are completed.
Resins having good color tone are obtained by carrying out the adjustment as mentioned above.
The lower limit of concentration of catalyst can be lowered so long as no trouble occurs, but usually it is kept 0.001 mass % or more.
Further, in the above range of concentration of catalyst, effect of moisture on color tone is great, therefore it is necessary to keep the concentration of moisture in a reaction system 100 ppm or less. Hydroxyl group-containing aromatic compound such as phenol is liable to absorb moisture owing to its polar groups. Exemplified as a method for dehydration is, for example, formation of azeotropic mixture of hydroxyl group-containing aromatic compound, with aromatic hydrocarbon such as toluene or other organic solvents such as oxygen-containing compounds. However, a reaction system absorbs moisture actually sometimes in a process of dehydration, therefore sufficient care is needed for dehydration. Further, it is necessary to dehydrate unsaturated cyclic hydrocarbon and the like before use by conventional procedure.
During a reaction period, usually gas in a reaction vessel is replaced by an inert gas, therefore it is preferable to use an airtight system. When an open system is used for reaction, reaction can be conducted while an inert gas is supplied to a reactor. As inert gases to be used herein, nitrogen, argon and the like are exemplified.
As above, it is most important to adjust the amount of moisture in a reaction system to 100 ppm or less. The amount of moisture must be confirmed by measuring a sample taken from the system.
In producing phenol resins, when an excess of hydroxyl group-containing aromatic compound is used compared with unsaturated cyclic hydrocarbon, the reaction between them can be carried out without solvent. Solvents can be also used, and they are not specially limited as long as they do not hinder the reaction. As preferable solvents, there are aromatic hydrocarbon compounds such as benzene, toluene and xylene.
The amount of solvent to be used is preferably 20-300 mass parts against 100 mass parts of the hydroxyl group-containing aromatic compound.
Temperature of the reaction is in the range of 20-170xc2x0 C., preferably 50-150xc2x0 C. If temperature of reaction exceeds 170xc2x0 C., decomposition of catalyst or side reaction occurs. If it is lower than 20xc2x0 C., reaction requires longer time uneconomically. Both cases are not desirable.
Though reaction time is not specially limited, it can be usually selected appropriately from the range of 10 minute to 60 hours.
In a method for producing a phenol resin of the present invention, it is enough only to react hydroxyl group-containing aromatic compound with unsaturated cyclic hydrocarbon under the conditions as above, and definite reaction procedures are not specified. For example, the following method can be used.
That is, hydroxyl group-containing aromatic compound, if necessary, with a prescribed organic solvent, is supplied to a reactor, then heated to form an azeotropic mixture and to remove an organic solvent and moisture. It is confirmed that the amount of water content in the system attains to a prescribed value. For this confirmation, usually the liquid can be taken out of the system and measured. After that, a prescribed amount of Friedel-Crafts catalyst is added in the system, then unsaturated cyclic hydrocarbon is added dropwise. Because it is also necessary to adjust the water content of unsaturated cyclic hydrocarbon, it is preferable to measure the water content previously and carry out dehydration according to conventional procedure.
After phenol resin is produced as mentioned above, deactivation of catalyst is carried out.
Though procedure for deactivation is not specially restricted, it is preferable to use the procedure in which the amount of the remaining ionic impurity, such as boron and fluorine, in a final phenol resin is 100 ppm or less. For this purpose, alkali metal, alkaline earth metal, and their oxides, hydroxide and carbonate, and inorganic bases such as ammonium hydroxide and ammonium gas can be used as deactivating agents. It is, however, preferable to use hydrotalcite, because the treatment is simple and prompt, and moreover, the amount of the remaining ionic impurity after treatment is small.
After acid catalyst is deactivated with or adsorbed by hydrotalcite or the like, the hydrotalcite having acid catalyst adsorbed are filtered off to recover the reaction liquid that does not substantially contain the residue of catalyst. Then, the reaction liquid can be condensed by distillation to obtain a hydrocarbon phenol resin of high purity. In carrying out filtration, operating efficiency can be improved by adding solvents or increasing temperature of the filtration feed.
The color estimation method (JIS K 5400) using Gardner standard solution, which has been known as a color estimation method for resin, is originally a method for estimating colors of liquid such as solution. Accordingly, the results are often inconsistent with colors of actual solid resins. Moreover, because the measurement is based on comparison with the standard color liquid, judgement standards differ according to persons taking measurements to cause variation of the results. On the contrary, with the method using absorptiometry in the region of visible rays and ultraviolet rays, variation of the results is small and correlation between measured values and actual colors is good. Therefore, the latter has been adopted as the color estimation method.
In measurement by absorptiometry, resins are dissolved in arbitrary solvents and diluted solutions are used. As diluting solvents, those that have small absorbency over the whole region of visible rays and ultraviolet rays are preferable. Accordingly, aliphatic saturated hydrocarbon solvent, aliphatic saturated hydrocarbon ether or the like is used. However, dioxane, tetrahydrofuran and the like are especially favorable because of great solubility of resins. Usually, dioxane is desirable. Color is estimated with the absorbance measured at wavelength 350 nm.
The present phenol resin excellent in color has the most remarkable characteristic in the absorbance at wavelength 350 nm. That is, those that have the absorbance of 1.0 or lower in a solution of 2 mass % in dioxane are useful as raw material for producing epoxy resin in the following step.
The phenol resins obtained as above are used as raw material for epoxy resins, and also useful as hardening agent of epoxy resin for electrically insulating materials, particularly materials for sealing semiconductors or materials for laminates. Furthermore, they are excellent in outward appearance and marking property owing to their good color. However, the use is not especially restricted.
In the following, a method for producing epoxy resin excellent in color will be described.
The present epoxy resin having good color can be obtained by reacting the phenol resin excellent in color obtained as above with epihalohydrin in the presence of base catalyst to introduce glycidyl group.
The above reaction of introducing glycidyl group can be carried out by the conventional procedure. Definitely, for instance, the phenol resin is reacted with a glycidyl group-containing agent such as epichlorohydrin or epibromohydrin in the presence of base such as sodium hydroxide or potassium hydroxide, usually at 10 to 150xc2x0 C., preferably at 30 to 80xc2x0 C. Then, the reaction product is washed with water and dried to give an epoxy resin.
The amount of glycidyl group-containing agent is preferably 2 to 20 times, particularly 3 to 7 times as much as that of hydroxyl group of the phenol resin in molar equivalent.
During the reaction period, the progress of reaction can be hastened by removing water by azeotropic distillation with the glycidyl group-containing agent under reduced pressure.
When the present hydrocarbon epoxy resin is used in a field of electronic materials, sodium chloride as a by-product must be removed completely in the water-washing step. At this time, after glycidyl group-containing agents are recovered by distillation to concentrate the reaction solution, the concentrated product may be dissolved in a solvent and washed with water. As solvents used here, methyl isobutyl ketone, cyclohexanone, benzene, butyl cellosolve and so forth are preferable. Hydrocarbon epoxy resin is obtained by heating the washed concentrate to enrichment.
The epoxy equivalent (g-resin/gram equivalent-epoxy group) of epoxy resin is usually 200 to 500, preferably 250 to 450. If epoxy equivalent exceeds 500, cross-linking density decreases unfavorably.
The epoxy resins obtained as above are superior to conventional epoxy resins having similar structure in color, outward appearance and marking property. Further, the resins of which absorbance is 0.8 or lower by the above-mentioned measurement are good also in actual color preferably.
Because the epoxy resins are excellent in color, they are useful as epoxy resin composition materials for electrically insulating materials, particularly materials for sealing semiconductors and materials for laminates. However, the use is not restricted only to these, but also useful for powder paint, break shoe and so forth.
In the use of epoxy resins, well-known hardening agents can be used. That is, all the compounds that are commonly used as hardening agents for epoxy resins can be used, and there is no restriction in particular. Definitely exemplified are phenolic novolak resin, o-cresol novolak resin, bisphenol A novolak resin, bisphenol F novolak resin, phenol-dicyclopentadiene polyaddition resin, naphthol novolak resin, dihydroxynaphthalene novolak resin; polyhydric phenols having xylidene as connecting group; phenol-aralkyl resin; aliphatic amines such as diethylenetriamine or triethylenetetramine; aromatic amines such as m-phenylenediamine, diaminodiphenylmethane or diaminodiphenylsulfone; polyamide resin and its modified product; hardening agent comprised of acid anhydride such as maleic anhydride, phthalic anhydride, hexahydrophthalic anhydride or pyromellitic anhydride; potential hardening agent such as dicyandiamide, imidazole, boron trifluoride-amine complex or guanidine derivative, and so forth.
The epoxy resins obtained according to the present invention are useful as material for sealing semiconductors. As hardening agents for this use, the following two compounds are preferable. One is aromatic hydrocarbonformaldehyde resin such as phenol novolak resin, which is excellent in hardening property, molding characteristic, thermal resistance and so forth. The other is phenol-aralkyl resin such as the phenol resin by the present invention, which is excellent in hardening property, molding characteristic, low hygroscopicity and so on.
The amount of these hardening agents to be used is not especially restricted as long as it is enough to harden epoxy resins. However, it is preferable to select the amount so that the number of active hydrogen in hardening agent will be nearly equivalent to the number of epoxy group in the epoxy resin used.
Furthermore, in addition to the hardening agent, hardening accelerator can be used optionally. As the hardening accelerator, any of well-known conventional ones can be used. For example, phosphorus-containing compound, tertiary amine, imidazole, metal salt of organic acid, Lewis acid, amine complex and so forth are used. It is possible to use each of these singly, or to use two or more kinds of them jointly. As materials for sealing semiconductors, triphenylphosphine in phosphorus-containing compounds, DBU in amines, and the like are preferable, because they are excellent in hardening property, thermal resistance, electrical property, moisture-proofing reliability and so forth.
In using the epoxy resin obtained by the present invention, the other epoxy resins can be added together.
Other epoxy resins used here are not especially limited. For instance, bisphenol A glycidyl ether-type epoxy resin, bromophenol novolak-type epoxy resin, tetrabromobisphenol A-type epoxy resin, biphenyl-type epoxy resin, trihydroxyphenylmethane-type epoxy resin, tetrahydroxyphenylethane-type epoxy resin and the like are used. The amount of these epoxy resins is not particularly restricted.
Further, various well-known conventional additives, such as coloring agent, flame retarder, mold releasing agent and coupling agent, can be mixed appropriately as the occasion demands.
In preparing materials for molding from the epoxy resin obtained by the present invention, the method such as the following can be used. That is, epoxy resin, hardening agent, hardening accelerator and other additives are mixed into a fully homogeneous state with a mixer and so forth, then subjected to melting and kneading with a hot forming roll or a kneading machine, and crushed after injecting or cooling. The epoxy resins by the present invention are obtained as mentioned above, and their use is not particularly limited. For example, they are used as materials for sealing semiconductors and materials for substrate of printed wiring, insulating powder paint, materials for mold, materials for resist ink, interlaminar insulating materials of build-up type, glass fiber reinforced plastics, carbon fiber reinforced plastics, materials for paint, materials for adhesives and so forth. Moreover, the present epoxy resin may be combined with acrylate to give epoxy acrylate resin, or may be modified with silicone elastomer or CTBN elastomer to give rubber-modified epoxy resin.
Among these uses, the present materials are extremely useful as those for sealing semiconductors, because they are particularly excellent in solder crack resistance. Further, they are also useful as materials for substrate of printed wiring, which are excellent in color as well as in impregnating property, moisture-proofing property, adhering property and so forth. In the following, the materials for sealing semiconductors will be described in more detail.
For preparing materials for sealing semiconductors, inorganic fillers are compounded as essential component in addition to the epoxy resin and hardening agent.
Materials for sealing semiconductors obtained by the present invention satisfy all of the requirements, which include fluidity during molding in sealing semiconductors, hardening property, molding property, thermal resistance after hardening, and further, solder crack resistance in mounting on a printed substrate, and printing characteristic by a laser marking device.
Inorganic filler used for sealing semiconductors is an essential component, which not only increases the mechanical strength and hardness of cured materials, but also gives low moisture absorption and low coefficients of linear expansion, and moreover, increases solder crack resistance. The amount of inorganic filler is not specially restricted. However, when it is in the range of 80 to 95 mass % in the sealing material, the above characteristics are developed excellently. Particularly when the material is used for sealing semiconductors, the above range is preferable because solder crack resistance is remarkably raised. It deserves special mention that fluidity, molding property and so forth are not spoiled at all in the present invention, even if inorganic fillers are added in 80 mass % or more.
Though the kind of inorganic filler is not particularly limited, crushed silica, bead silica, alumina, talc, clay, glass fiber and so forth can be used. Among these, crushed silica and bead silica are generally used as materials especially for sealing semiconductors, and both fluidity during molding and strength of cured material can be improved in a good balance by using a mixture of crushed silica and bead silica. The mixture of crushed silica and bead silica both having the average diameter of 10 to 30 xcexcm improves particularly these characteristics.
Further, also in the use as materials for sealing semiconductors, other epoxy resin can be added to the epoxy resin of the present invention as mentioned above. As the other epoxy resin, flame-resistant one such as tetrabromobisphenol A-type epoxy resin and bromophenol epoxy resin like bromophenol novolak-type epoxy resin is particularly desirable.
Besides, as other components to be mixed, various additives can be used. They are as follows: flame resistant materials such as antimony trioxide and hexabromobenzene, coloring agents such as carbon black, iron oxide red and mica, mold releasing agents such as natural wax and synthetic wax, and low stress additives such as silicone oil, synthetic rubber and silicone rubber. Further, the above hardening accelerator can be also used preferably.
If necessary, various known conventional additives can be compounded appropriately, such as other kinds of coloring agent, flame retarder, mold releasing agent or coupling agent.
In preparing materials for molding from the epoxy resin obtained by the present invention, the method such as the following can be used. That is, epoxy resin, hardening agent, hardening accelerator and other additives are mixed into a fully homogeneous state with a mixer and so forth, then subjected to melting and kneading with a hot forming roll or a kneading machine, crushed after cooling and tabletted.
The resin-sealed semiconductor apparatuses fabricated with the material for sealing semiconductor obtained by the present invention can be printed using a laser-marking device, and the printed part develops color excellently. The shape of package of semiconductor apparatus is not especially restricted, and packages of all the shapes such as DIP, SOP, SOJ, QFP, BGA and CSP can be used. Laser marking device is not limited particularly either, and so devices such as YAG laser and carbon dioxide laser are utilized.